Sinonasal complaints affect at least 15% of the population in the United States of America with predictable patient morbidity and financial impact. Importantly, any modality that can alleviate sinonasal complaints warrants serious attention. Among various treatments utilized in this setting, nasal irrigation is considered a simple, inexpensive and beneficial approach that can be applied in concert with existing prescribed medications such as steroids, anti-histamines, vasoconstrictors and other drugs or as part of treatment modalities that help alleviate sinonasal symptoms such as nasal obstruction, rhinorrhea and others.
The principal functions of the nasal passages are the regulation of the inspiratory air flow, the heating and humidification of inspired air and the elimination of foreign elements (dust, microbial germs). The ciliate epithelium, which covers the nasal mucosa, plays a vital role in its defense from infections. The vibratile cilia of this epithelium are immersed in protective mucus, which surrounds them, and their purpose is to push this mucous, together with any external impurities, posteriorly, i.e., towards the pharynx, by their motions.
Seawater-based compositions currently available for rinsing the nasal passages are generally prepared so that they are isotonic with the nasal mucosa. These compositions usually consist of a mixture of seawater and deionized water, such that the per volume fraction of seawater in this mixture is approximately one-third. Alternatively, the compositions consist of increased per volume seawater fractions resulting in hypertonic solutions. These are believed to have better cleansing properties due to the generation of osmotic gradients that allow for more efficacious mucus removal in comparison to isotonic solutions.
However, and despite their widespread use for cleansing and symptomatic relief of sinonasal conditions, these solutions, typically packaged in the form of aerosol sprays, provide little or no therapeutic benefits against the causes of the disease. Furthermore, and in cases where the seawater compositions are complemented with additional ingredients thought to improve their action, such as exogenous salts, anti-septic anti-bacterial agents, amino acids, essential oils and other agents, they suffer from limited industrial applicability due to various factors. These include poor water solubility of added ingredients, label restrictions and/or burning sensations (e.g. in the case of essential oils; these cannot be used in children according to WHO guidelines), limited compatibility of added ingredients to the high salt content present in (hypertonic) solutions, increased cost or other limitations.
For this reason, better seawater and/or saline solutions with improved efficacy and negligible side effects are sought.